Energy integration of CO2 networks and Power to Gas for emerging energy autonomous cities in Europe

CO2 is used more and more as a refrigerant in the commercial and food retail industries and a majority of experts believe that its share in the field of residential heating, commercial refrigeration and mobile air conditioning across Europe will be higher than 20% by 2020. The concept of urban CO2 networks extends the approach developed by the refrigeration industry by bringing heat from the environment to neighbourhoods, similarly to tempered water district heating and cooling networks. However, unlike the water network, the CO2 network uses phase change to transfer heat between plants, interfacing the network with the environment and with the users. For each user, the heat is supplied/retrieved at the appropriate temperature, by connecting the best suited energy conversion technology. Besides its capacity to harvest and distribute heat from the environment (sun, underground, lake/river or waste heat), the CO2 network turns into a multi-energy power to gas system when coupled with a solid oxide fuel cell-solid oxide electrolysis cell system. The present work compares the integration of CO2 district energy network - power to gas systems for typical urban areas in 4 different climate zones across Europe. The system studied is fully energy autonomous, using renewable energy sources represented by PV panels and municipal and industrial waste heat.